Monitoring the load of a wind energy plant

ABSTRACT

The present invention concerns an apparatus for monitoring a wind power installation, with at least one sensor for detecting measurement values, and also a method of monitoring a wind power installation, in which a) a measurement value is detected with at least one sensor, b) said measurement value is converted into a signal representative of the measurement value, and c) the signal is stored and/or processed in accordance with a predetermined method. In order to provide an apparatus and a method which permit reliable detection of the loading on the pylon of the wind power installation, there is provided at least one sensor  20  for detecting the loading on the pylon  10,  the sensor  20  being arranged in the region of the base of the pylon. In addition, the instantaneous loading on the wind power installation is ascertained from the signal representative of the measurement value ascertained by the sensor.

[0001] The present invention concerns a wind power installation having a monitoring apparatus, with at least one sensor for detecting measurement values, and also a method of monitoring a wind power installation, in which a) a measurement value is detected with at least one sensor, b) said measurement value is converted into a signal representative of the measurement value, and c) the signal is stored and/or processed in accordance with a predetermined method.

[0002] Such apparatuses and methods are known in the state of the art. The journal ‘Erneuerbare Energien’ [‘Renewable Energies’], issue July 2000, page 38, which appeared at SunMedia Verlags- und Kongressgesellschaft für Erneuerbare Energien mbH Hannover, in an article entitled ‘Knackt der Rotor den Turm’ [‘The rotor roughs up the pylon’], mentions oscillation monitoring by means of acceleration measurement.

[0003] Issue No May 2000 of that journal, in paragraph 2 on page 37 thereof, describes that the oscillation monitors which are nowadays offered by several manufacturers involve acceleration pickups. Also described therein is a method in which dangerous frequencies are deliberately and specifically amplified by means of an electronic system.

[0004] That state of the art permits detection of oscillations of the head of the pylon in certain frequency ranges. Those oscillations form a part of the loadings on the pylon. In that respect the pylon is designed for a predetermined total of loadings during its intended service life of for example 20 years.

[0005] Each loading makes a contribution to material fatigue. It is therefore easy to understand that, at locations with a large number of high loadings, fatigue progresses more quickly than at locations with few and low loadings.

[0006] This therefore involves a differing ‘mechanical’ age, with an assumed identical age of the pylons in terms of time. In that respect, it can happen that, when reaching its age limit in terms of time of 20 years, the pylon which has been subjected to lower levels of loading has mechanically only experienced a loading which, in regard to the design thereof, was already intended after 15 years, so that the pylon can certainly still remain in operation. It will be appreciated that the reverse situation is also conceivable, in which a pylon has already reached a mechanical age of 20 years, after just 15 years.

[0007] With the previous arrangements, the mechanical service age of a pylon can still not be adequately detected, so that ultimately it is only possible to arrive at vague estimates about the service life of a pylon and thus one of the most important parts of the wind power installation.

[0008] The object of the invention is to provide an apparatus and a method which permits reliable detection of the loading on the wind power installation and a reliable estimate of important parts of the wind power installation.

[0009] In accordance with the invention that object is attained with a wind power installation having the feature of claim 1. Advantageous developments are set forth in the appendant claims.

[0010] The invention is based on the realisation that all loads which occur at a wind power installation act on the pylon of the installation. If the base of the pylon has experienced half the load collective, the other components such as blades, machine carrier, head of the pylon, pylon etc, can scarcely have experienced a significantly higher proportion of the load collective.

[0011] Ultimately, the load at the base of the pylon cannot correspond to a situation involving a wind speed of for example 4 m/s while the load at other components corresponds for example to a wind speed of 8 m/s. Therefore, detecting the loading on the pylon makes it possible to arrive at a conclusion about the loadings to which the wind power installation is overall exposed at its site.

[0012] As, in a simplification, the wind power installation can be viewed as a bar which is gripped at one end, it is possible to detect the sum of all loads acting on the wind power installation, at the base of the pylon. Arranging at least one sensor in the region of the base of the pylon therefore permits reliable detection of the loading on the wind power installation. At the same time it is possible to reach the sensor without aids and without involving a high degree of expenditure and complication.

[0013] In a preferred embodiment of the invention detection of the loading is effected by a sensor based on a RSG (resistance strain gauge). The loading can be reliably detected by means of such a sensor, with an adequate degree of accuracy, using tried and tested technology.

[0014] The measurement values detected by the resistance strain gauge are particularly preferably converted into analog or digital electrical signals which are representative of the measurement values. Those signals can be transmitted and subjected to further processing in a simple manner.

[0015] Such further processing can be a comparison with a limit value in order for example to be able to recognise load maxima or to ascertain when predeterminable load limits are reached or exceeded. In addition the measurement values can be cumulated and stored for subsequent processing or evaluation.

[0016] It will be appreciated that the result of the cumulation can also in turn be compared to a predeterminable limit value. In that way it is possible to consider the loading on the installation in relation to the design loads and thus to implement an estimate of the mechanical service age of the installation.

[0017] In addition the method as referred to in the opening part of this specification is developed in such a way that the instantaneous loading on the wind power installation is ascertained from the signal from the sensor. As, in extensive measurements on the prototype of a wind power installation, the correlation of the load situations at various components of the wind power installation is also ascertained, data are available, which make it possible to draw a conclusion, from the load at the base of the pylon, about the load on the other components. By virtue of cumulation of all the ascertained loadings it is possible to ascertain the overall loading on the wind power installation and thus its mechanical service age.

[0018] By virtue of a correlation of the instantaneous loading with the instantaneous wind, it is possible to check whether the ascertained instantaneous loading on the wind power installation corresponds to an approximately expected order of magnitude. It is possible in that manner to monitor satisfactory functioning of the apparatus according to the invention.

[0019] The measured loading data can also be subjected to further processing in a control apparatus of the wind power installation in such a way that, when an overload occurs, the control apparatus implements measures which result in a reduction in the loading. Such a reduction in loading can be effected for example by adjustment of the rotor blades (out of the wind) or also by a reduction in the speed of rotation of the rotor of the wind power installation. In addition the entire rotor of the wind power installation could be rotated out of the wind through a given angle, to reduce the loading.

[0020] The method according to the invention results in a detailing of the load total which has been experienced to date by the wind power installation, in relation to the design loads. That relationship, like also individual measurement values and/or the cumulated loading, can be stored and/or processed in the installation. In addition those data can be for example regularly transmitted to a remote location such as a remote monitoring system, or called up therefrom.

[0021] An embodiment of the invention by way of example thereof is described hereinafter. In the drawing:

[0022]FIG. 1 is a simplified view of a wind power installation,

[0023]FIG. 2 shows an arrangement of sensors, and

[0024]FIG. 3 shows a flow chart of the method according to the invention.

[0025]FIG. 1 shows a pylon 10 of a wind power installation, which is connected to a foundation 12. Arranged at the head of the pylon 10 is a pod 14 which has a rotor which rotor blades 16. In this Figure the arrow denotes the direction of the wind.

[0026] The wind rotates on the one hand the rotor and therewith the subsequently mechanically coupled part of the wind power installation in order to generate electrical energy. At the same time however on the one hand the pylon 10 is subjected to the effect of the pressure of the wind and on the other hand the pod 14 with the rotor is deflected in the direction of the wind. As a result, a bending moment occurs at the pylon 10 which is gripped at one end, over the lever arm of the length of the pylon, at the foundation 12.

[0027] The effect of the force acting on the head of the pylon produces a force pattern over the entire length of the pylon so that the alternating loads or oscillations cause a corresponding material fatigue effect.

[0028]FIG. 2 shows an arrangement of two sensors 20 in the region of the base of the pylon. Those sensors 20 can operate for example on the basis of RSGs (resistance strain gauges) and detect the stress at the base of the pylon. That stress permits a quite accurate conclusion to be drawn about the overall stress on the wind power installation. Instead of the arrangement of only two sensors it may also be advantageous under some circumstances to arrange a plurality of sensors distributed around the periphery of the base of the pylon in order in that way to afford sensors for a plurality of main wind directions, in such a fashion that the sensors can ascertain the respective maximum tensile/compression loadings which occur on the base of the pylon.

[0029] In addition the signals/data ascertained with the sensors can be subjected to further processing in a control apparatus of the wind power installation (not shown) in such a way that, when predetermined maximum values are exceeded once, a plurality of times or in a time-wise manner, the overall loading on the wind power installation is reduced, by a procedure such that for example the speed of rotation of the rotor of the wind power installation is reduced by means of the control system and/or the individual rotor blades are rotated out of the wind through a given angle, thereby reducing the loading which acts due to the rotor or the effect of the wind acting thereon.

[0030] The second device 40 can detect the electrical signals and evaluate or process them. The measurement values can be compared for example to a first limit value which marks a predetermined load limit. If the measurement value reaches or exceeds that first limit value, a signal can be triggered, which displays precisely that.

[0031] If the limit value, that is to say in the present example a load limit, is reached/exceeded in that way repeatedly, that makes it possible to conclude that there is a systematic deviation from load assumptions which have been previously made. Thereupon it is possible to restrict the cause thereof, for example incorrect control of the wind power installation or an extreme situation which is dependent on the site of the installation, so that it is possible to produce a remedy in that respect.

[0032] Mechanical ageing of the pylon can be constantly monitored by continued cumulative recording and continuous comparison with the design loads.

[0033] Storage of the load data also has the advantage that, in the event of damage possibly occurring to the pylon of the wind power installation, it is more easily possible to obtain proof of whether given overload phases have occurred and whether the maximum loadings occurring were complied with.

[0034] Finally, it is also advantageous if the measured load data of a wind power installation are acquired centrally and, in the event that the measured load data frequently or constantly exceed a given maximum value, measures can be implemented on the part of the operator in good time, to prevent premature mechanical ageing of the pylon. Such a measure for example may also involve strengthening certain elements of the wind power installation, including for example the pylon.

[0035] Instead of a resistance strain gauge, for detecting the loading it is also possible to use any other device by means of which tensile forces and/or compression forces and/or torsion forces and/or oscillations or the amplitudes thereof in the pylon and in particular the top of the pylon of a wind power installation can be detected.

[0036]FIG. 3 shows a flow chart of a method according to the invention. The procedure begins with the step 50 and the measurement value is detected in step 51. In step 52 the detected measurement value is compared to a first limit value. If the measurement value exceeds that first limit value, it is precisely this that is indicated in step 53. If the measurement value does not exceed the first limit value the procedure misses out step 53.

[0037] In step 54 the measurement values are cumulated so that the overall loading experienced by the wind power installation to date is ascertained. That overall loading is related to the design loads in step 55. It is possible to read therefrom the mechanical service age, that is to say the load collective already experienced by the wind power installation, in relation to the design load collective. That relationship is represented in step 56 before the procedure terminates with step 57.

[0038] The representation can be effected for example after data transmission in a central remote monitoring station or at the operator of the wind power installation and can be in the form of a bar chart, a pie chart or any other suitable form of representation. 

1. A wind power installation having an apparatus for monitoring the loading on parts of the wind power installation or the entire wind power installation, wherein the apparatus is arranged in the region of the base of the pylon of the wind power installation and has means with which the loadings on the pylon can be measured in the region of the base of the pylon, characterised in that the wind power installation has a control device which processes the data to be measured for detecting the loading on the pylon and which controls the wind power installation in such a way that a reduction in the speed of rotation of the rotor of the wind power installation and/or a reduction in the loading on the wind power installation is effected by means of adjustment of the rotor blades when the measured data exceed a given maximum value once, a plurality of times and/or over a certain period of time.
 2. A wind power installation according to claim 1 characterised in that the apparatus for detecting the loading on the pylon in the region of the base thereof is a sensor based on resistance strain gauges (RSGs).
 3. A wind power installation according to one of the preceding claims characterised by a first device (30) for converting the detected measurement values (detected by the sensor (20)) into analog or digital electrical signals which are representative of the measurement values.
 4. Apparatus according to claim 3 characterised by a second device (40) for detecting the electrical signals and for comparing the measurement value represented by the signal to at least one predeterminable first limit value and for displaying when the limit value is reached or exceeded; and/or for storing and/or cumulating the measurement values represented by the electrical signal.
 5. Apparatus according to one of the preceding claims characterised by a device for the transmission of signals which represent individual measurement values and/or the cumulated measurement values and/or a relationship of the cumulated measurement values with a predeterminable second limit value.
 6. A method of monitoring a wind power installation in which data for the loading on the wind power installation are detected by means of a measurement value data pickup, the measurement value data are stored and/or processed in accordance with a predetermined method, and the instantaneous loading on the overall wind power installation is ascertained from the measurement value data.
 7. A method according to claim 6 characterised in that the ascertained instantaneous loadings are cumulated.
 8. A method according to claim 6 characterised in that the ascertained instantaneous loadings are correlated with the instantaneously measured wind.
 9. A method according to one of claims 6 to 8 characterised in that the measurement value is compared to a predeterminable first limit value and attainment or exceeding of the limit value is displayed.
 10. A method according to one of claims 7 to 9 characterised in that the cumulated measurement values are related to a predeterminable second limit value.
 11. A method according to claim 10 characterised in that the relationship between the cumulated measurement values and the second limit value is represented. 